Conveying system for a vacuum processing apparatus

ABSTRACT

A vacuum processing apparatus which includes a cassette mount table for holding at least one cassette, a conveying structure that includes a robot, a cassette table for holding the cassette, an additional conveying structure for transferring a wafer held on the cassette table. Further, the apparatus is provided with a vacuum loader which is connected to the additional conveying device by a lock chamber. a controller system controls the second conveyor structure and manages the replacement of the cassette on the cassette table; and further, instructs the replacement of the cassette.

This application is a Divisional application of Ser. No. 09/766,587,filed Jan. 23, 2001, which is a Divisional application of applicationSer. No. 09/461,432, filed Dec. 16, 1999, now U.S. Pat. No. 6,330,755which is a Continuation application of application Ser. No. 09/177,495,filed Oct. 23, 1998, now U.S. Pat. No. 6,012,235 which is a Continuationapplication of application Ser. No. 09/061,062, filed Apr. 16, 1998, nowU.S. Pat. No. 5,950,330 which is a Continuation application ofapplication Ser. No. 08/882,731, filed Jun. 26, 1997, now U.S. Pat. No.5,784,799 which is a Divisional application of application Ser. No.08/593,870, filed Jan. 30, 1996, now U.S. Pat. No. 5,661,913 which is aContinuing application of application Ser. No. 08/443,039, filed May 17,1995, now U.S. Pat. No. 5,553,396 which is a Divisional application ofapplication Ser. No. 08/302,443, filed Sep. 9, 1994, now U.S. Pat. No.5,457,896 which is a Continuing application of application Ser. No.08/096,256, filed Jul. 26, 1993, now U.S. Pat. No. 5,349,762 which is aContinuing application of application Ser. No. 07/751,952, filed Aug.29, 1991 now abandon.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to a vacuum processing apparatus and operatingmethod therefore More specifically, the present invention relates to avacuum processing apparatus having vacuum processing chambers the insideof which must be cleaned, and its operating method.

Description of the Prior Art

In a vacuum processing apparatus such as a dry etching apparatus, a CVDapparatus or a sputtering apparatus, a predetermined number ofsubstrates to be treated are stored as one unit (which is generallyreferred to as a “lot”) in a substrate cassette and are loaded in theapparatus. The substrates after being processed are likewise stored inthe same unit in the substrate cassette and are recovered. This is anordinary method of operating these apparatuses to improve theproductivity.

In such a vacuum processing apparatus described above, particularly inan apparatus which utilizes a reaction by an active gas, as typified bya dry etching apparatus and a CVD apparatus, reaction products adhere toand are deposited on a vacuum processing chamber with the progress ofprocessing. For this reason, problems such as degradation of vacuumperformance, the increase of dust, the drop of the levels of opticalmonitoring signals occur. To solve these problems, conventionally theinsides of the vacuum processing chambers are cleaned periodically.Cleaning operations include so-called “Wet cleaning” which is wiping-offor the adhering matters by use of an organic solvent, etc., andso-called “dry cleaning” in which an active gas or plasma is used fordecomposing adhering matters- Dry cleaning is superior from the aspectof the working factor and efficiency. These features of the dry cleaninghave become essential with the progress in automation of productionlines.

An example of vacuum processing apparatuses having such a dry cleaningfunction is disclosed in Japanese Utility Model Laid-Open No.127125/1988. This apparatus includes a preliminary vacuum chamber forintroducing wafers to be treated into a processing chamber from anatmospheric side to a vacuum side, which is disposed adjacent to theprocessing chamber through a gate valve, dummy wafers are loaded in thepreliminary vacuum chamber and are transferred into the processingchamber by exclusive conveyor means before the processing chamber issubjected to dry cleaning, and the dummy wafer is returned to the vacuumpreparatory chamber by the conveyor means after dry cleaning iscompleted.

SUMMARY OF THE INVENTION

In the prior art technology described above, the structure of the vacuumprocessing apparatus is not much considered. The preliminary vacuumchamber for storing the dummy wafers must have a large capacity, theexclusive conveyor means is necessary for transferring the dummy wafersand thus, the apparatus is complicated in structure.

Dummy wafers used for plasma cleaning are again returned to thepreliminary vacuum chamber and are made to stand by. In this instance,reaction products generated during plasma cleaning and residual gas usedfor plasma cleaning adhere on the used dummy wafers. Thereafter, normalprocessing for wafers is resumed. Therefore, the used dummy wafers andunprocessed wafers exist in mixture inside the preliminary vacuumchamber and this state is not desirable from the aspect of contaminationof unprocessed wafers.

The present invention provides a vacuum processing apparatus whichsolves the problems described above, is simple in structure, preventscontamination of unprocessed substrates and accomplishes a highproduction yield A vacuum processing apparatus having vacuum processingchambers the insides of which are dry-cleaned after substrates to betreated are processed in vacuum is provided with first storage means forstoring substrates to be treated, second storage means for storing dummysubstrates, the first and second storage means being disposed in theair, conveyor means for transferring the substrates to be processedbetween the first storage means and the vacuum processing chambers andfor transferring the dummy substrates between the second storage meansand the vacuum processing chambers, and control means for controllingthe conveyor means so as to transfer the dummy substrates between thesecond storage means and the vacuum processing chambers before and afterdry cleaning of the vacuum processing chambers. A method of operating avacuum processing apparatus having vacuum processing chambers theinsides of which are dry-cleaned after substrates to be processed areprocessed in vacuum comprises the steps of disposing first storage meansfor storing the substrates to be processed together with second storagemeans for storing dummy substrates in the air atmosphere, transferringthe substrates to be processed between the first storage means and thevacuum processing chambers and vacuum-processing the substrates to beprocessed, and transferring the dummy substrates between the secondstorage means and the vacuum processing chambers before and afterdry-cleaning of the vacuum processing chambers

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a dry etching apparatus as an embodiment of avacuum processing apparatus in accordance with the present invention;and

FIG. 2 is a vertical sectional view taken along line 1—1 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As substrates to be processed are processed in a vacuum processingapparatus, reaction products adhere to and are deposited in vacuumprocessing chambers. The reaction products adhering to and deposited inthe vacuum processing chambers are removed by disposing dummy wafersinside the vacuum processing chambers and by conducting dry-cleaning. Tocarry out dry cleaning, the timings of dry cleaning of the vacuumprocessing chambers are determined and during or after the processing ofa predetermined number of substrates to be processed, dummy substratesare conveyed by substrate conveyor means from dummy substrate storagemeans disposed in the air atmosphere together with processed substratestorage means, and are then disposed inside the vacuum processingchambers After the dummy substrates are thus disposed, a plasma isgenerated inside each of the vacuum processing chambers to executedry-cleaning inside the vacuum processing chamber. After dry-cleaninginside the vacuum processing chambers is completed, the dummy substratesare returned from the vacuum processing chambers to the dummy substratestorage means by the substrate conveyor means. In this manner, 3preliminary vacuum chamber and an exclusive transfer mechanism bothnecessary in prior art techniques become unnecessary, and the apparatusstructure gets simplified. The dummy substrates used for thedry-cleaning and the substrates to be processed do not co-exist insidethe same chamber, so that contamination of substrates to be processeddue to dust and remaining gas is prevented and a high production yieldcan be achieved.

Hereinafter, an embodiment of the present invention will be explainedwith reference to FIGS. 1 and 2.

FIGS. 1 and 2 show a vacuum processing apparatus of the presentinvention which is, in this case, a dry-etching apparatus for etchingwafers, i.e., substrates to be processed by plasma.

Cassette tables 2 a to 2 c are disposed in an L-shape in this case inpositions such that they can be loaded into and unloaded from theapparatus without changing their positions and postures. In other words,the cassettes 1 a to 1 c are fixed always in predetermined positions ona substantially horizontal plane, while the cassette tables 2 a and 2 bare disposed adjacent to and in parallel with each other on one of thesides of the L-shape The cassette table 2 c is disposed on the otherside of the L-shape. The cassettes 1 a and 1 b are for storingunprocessed wafers and for recovering the processed wafers. They canstore a plurality (usually 25) of wafers 20 as the substrates to betreated. The cassette 1 c in this case is for storing the dummy wafersfor effecting dry-cleaning using plasma (hereinafter referred to as“plasma-cleaning”) and recovering the dummy wafers afterplasma-cleaning. It can store a plurality of (usually twenty-fivepieces) dummy wafers 30.

A load lock chamber 5 and unload lock chamber 6 are so disposed as toface the cassette tables 2 a and 2 b, and a conveyor 13 is disposedbetween the cassette tables 2 a, 2 b and the load lock chamber 5 and theunload lock chamber 6. The load lock chamber 5 is equipped with anevacuating device 3 and a gas introduction device 4, and can loadunprocessed wafers in the vacuum apparatus through a gate valve 12 a.The unload lock chamber 6 is similarly equipped with the evacuatingdevice 3 and the gas introduction device 4, and can take out processedwafers to the atmosphere through a gate valve 12 d. The conveyor 13 isequipped with a robot having X, Y, Z and— axes, which operates so as todeliver and receive the wafers 20 between the cassettes 1 a, 1 b and theload lock and unload lock chambers 5 and 6 and the dummy wafers 30between the cassette 1 c and the load lock and unload lock chambers 5and 6.

The load lock chamber 5 and the unload lock chamber 6 are connected to atransfer chamber 16 through the gate valves 12 b and 12 c. The transferchamber 16 is rectangular, in this case, and etching chambers 11 a, 11 band 11 c are disposed on the three side walls of the transfer chamber 16through gate valves 15 a, 15 b and 15 c, respectively. A conveyor 14capable of delivering the wafers 20 or the dummy wafers 30 from the loadlock chamber 5 to the etching chambers 11 a, 11 b, 11 c and ofdelivering them from the chambers 11 a, 11 b, 11 c to the unload lockchamber 6 is disposed inside the transfer chamber 16. The transferchamber 16 is equipped with an evacuating device 17 capable ofindependent evacuation.

The etching chambers 11 a, 11 b, 11 c have the same structure and canmake the same processing. The explanation will be given on the etchingchamber 11 b by way of example. The etching chamber 11 b has a sampletable 8 b for placing the wafers 20 thereon, and a discharge chamber isso provided as to define a discharge portion 7 b above the sample table8 b. The etching chamber 11 b includes a gas introduction device 10 bfor introducing a processing gas in the discharge portion 7 b and anevacuating device 9 b for decreasing the internal pressure of theetching chamber 11 b to a predetermined pressure. The etching chamber 11b further includes generation means for generating a microwave and amagnetic field for converting processing gas in the discharge portion 7b to plasma.

A sensor 18 for measuring the intensity of plasma light is disposed atan upper part of the etching chamber. The measured value of the sensor13 is inputted to a controller 19 The controller 19 compares themeasured value from the sensor 18 with a predetermined one anddetermines the timing of cleaning inside the etching chamber. Thecontroller 19 controls the conveyors 13 and 14 to control the transferof the dummy wafers 30 between the cassette 1 c and the etching chambers11 a to 11 c.

In a vacuum processing apparatus having the construction describedabove, the cassettes 1 a, 1 b storing unprocessed wafers are firstplaced onto the cassette tables 2 a, 2 b by a line transfer robot whichoperates on the basis of the data sent from a host control apparatus, orby an operator. On the other hand, the cassette 1 c storing the dummywafers is placed on the cassette table 2 c. The vacuum processingapparatus executes the wafer processing or plasma cleaning on the basisof recognition by itself of the production data provided on thecassettes 1 a to 1 c, of the data sent from the host control apparatus,or of the command inputted by an operator

For instance, the wafers 20 are sequentially loaded in the order fromabove into the etching chambers 11 a, 11 b, 11 c by the conveyors 13 and14, and are etched. The etched wafers are stored in their originalpositions inside the cassette 1 a by the conveyors 14 and 13. In thiscase, from the start to the end of the operation, without changing theposition and posture of the cassettes, the unprocessed wafers are takenout from the cassettes and are returned in their original positionswhere the wafers have been stored, and are stored there. In this manner,the apparatus can easily cope with automation of the production line,contamination of the wafers due to dust can be reduced and highproduction efficiency and high production yield can thus beaccomplished.

As etching is repeated, the reaction products adhere to and aredeposited on the inner wall of the etching chambers 11 a to 11 c.Therefore, the original state must be recovered by removing the adheringmatters by plasma cleaning. The controller 19 judges the timing of thisplasma cleaning. In this case, a portion through which the plasma lightpasses is provided in each of the etching chambers 11 a to 11 c. Thesensor 18 measures the intensity of the plasma light passing throughthis portion and when the measured value reaches a predetermined one,the start timing of plasma cleaning is judged Alternatively, the timingof plasma cleaning may be judged by counting the number of wafersprocessed. In each etching chamber by the controller 19 and judging thetiming when this value reaches a predetermined value. The actual timingof plasma cleaning that is carried out may be during a processing of apredetermined number of wafers in the cassette 1 a or 1 b, after theprocessing of all the wafers 20 in a cassette is completed and beforethe processing of wafers in the next cassette

Plasma cleaning is carried out in the following sequence In this case,the explanation will be given about a case where the etching chambers 11a to 11 c are subjected to plasma cleaning by using three dummy wafers30 among the dummy wafers 30 (twenty-five dummy wafers are stored inthis case) stored in the cassette 1 c.

Dummy wafers 30 which are stored in the cassette 1 c and are not usedyet or can be used because the number of times of use for plasmacleaning is below a predetermined one are drawn by the conveyor 13. Atthis time, dummy wafers 30 stored in any position in the cassette 1 cmay be used but in this case, the position numbers of the dummy wafersin the cassette and their number of times of use are stored in thecontroller 19, and accordingly dummy wafers having smaller numbers oftimes of use are drawn preferentially. Then, the dummy wafers 30 areloaded in the load lock chamber 5 disposed on the opposite side to thecassette 1 a by the conveyor 13 through the gate valve 12 a in the sameway as the transfer at the time of etching of wafers 20. After the gatevalve 12 a is closed, the load lock chamber 5 is evacuated to apredetermined pressure by the vacuum exhaust device 3 and then the gatevalves 12 b and 15 a are opened. The dummy wafers 30 are transferred bythe conveyor 14 from the load lock chamber 5 to the etching chamber 11 athrough the transfer chamber 16 and are placed on the sample table 8 a.After the gate valve 15 a is closed, plasma cleaning is carried out inthe etching chamber 11 a in which the dummy wafers 30 are disposed,under a predetermined condition

In the interim, the gate valves 12 a, 12 b are closed and the pressureof the load lock chamber 5 is returned to the atmospheric pressure bythe gas introduction device 4. Next, the gate valve 12 a is opened andthe second dummy wafer 30 is loaded in the load lock chamber 5 by theconveyor 13 in the same way as the first dummy wafer 30, and evacuationis effected again by the evacuating device 3 to a predetermined pressureafter closing the gate valve 12 a. Thereafter, the gate valves 12 b and15 b are opened and the second dummy wafer 30 is transferred from theload lock chamber 5 to the etching chamber 11 b through the transferchamber 16 by the conveyor 14. Plasma cleaning is started after the gatevalve 15 b is closed.

In the interim, the third dummy wafer 30 is transferred into the etchingchamber 11 c in the same way as the second dummy wafer 30 and plasmacleaning is carried out.

After plasma cleaning is completed in the etching chamber 11 a in whichthe first dummy wafer 20 is placed, the gate valves 15 a and 12 c areopened. The used dummy wafer 30 is transferred from the etching chamber11 a to the unload lock chamber 6 by the conveyor 14 Then, the gatevalve 12 c is closed. After the pressure of the unload lock chamber 6 isreturned to the atmospheric pressure by the gas introduction device 4,the gate valve 12 d is opened The used dummy wafer 30 transferred to theunload lock chamber 6 is taken out in the air by the conveyor 13 throughthe gate valve 12 d and is returned to its original position in thecassette 1 c in which it is stored at the start.

When plasma cleaning of the etching chambers 11 b and 11 c is completed,the second and third dummy wafers 20 are returned to their originalpositions in the cassette 1 c.

In this way, the used dummy wafers 30 are returned to their originalpositions in the cassette 1 c and the dummy wafers 30 are always stockedin the cassette 1 c. When all the dummy wafers 30 in the cassette 1 care used for plasma cleaning or when the numbers of times of use of thewafers 30 reach the predetermined ones after the repetition of use, thedummy wafers 30 are replaced as a whole together with the cassette 1 c.The timing of this replacement of the cassette is managed by thecontroller 19 and the replacement is instructed to the host controlapparatus for controlling the line transfer robot or to the operator.

Although the explanation given above deals with the case where theetching chambers 11 a to 11 c are continuously plasma-cleaned by the useof three dummy wafers 30 among the dummy wafers 30 in the cassette 1 c,other processing methods may be employed, as well.

For example, the etching chambers 11 a to 11 c are sequentiallyplasma-cleaned by the use of one dummy wafer 30. In the case of suchplasma cleaning, unprocessed wafers 20 can be etched in etching chambersother than the one subjected to plasma cleaning, and plasma cleaning canthus be carried out without interrupting etching.

If the processing chambers are different, for example, there are anetching chamber, a post-processing chamber and a film-formation chamber,and wafers are sequentially processed while passing through each ofthese processing chambers, each of the processing chambers can besubjected appropriately to plasma cleaning by sending dummy wafers 30during the processing of the wafers 20 which are stored in the cassette1 a or 2 a and drawn and sent sequentially, by passing merely the dummywafers 30 through the processing chambers for which plasma cleaning isnot necessary, and by executing plasma cleaning only when the dummywafers 30 reach the processing chambers which need plasma cleaning

According to the embodiment described above, the cassette storing thedummy wafers and the cassettes storing the wafers to be processed aredisposed together in the air, the dummy wafers are loaded from thecassette into the apparatus by the same conveyor as the conveyor fortransferring the wafers, at the time of cleaning, and the used dummywafers are returned to their original positions in the cassette. In thisway, a mechanism for conducting exclusively plasma cleaning need not beprovided, and the construction of the apparatus can be simplified. It isnot necessary to handle plasma cleaning as a particular processingsequence, but the plasma cleaning can be incorporated in an ordinaryetching processing and can be carried out efficiently in a series ofoperations.

The dummy wafers used for plasma cleaning are returned to their originalpositions in the cassette placed in the air. Accordingly, the used dummywafers and the wafers before and after processing do not exist mixedlyin the vacuum chamber, so that contamination of wafers due to dust andremaining gas does not occur unlike conventional apparatuses.

The used dummy wafers are returned to their original positions in thecassette and the numbers of times of their use is managed. Accordingly,it is possible to prevent the confusion of the used dummy wafers withthe unused dummy wafers and the confusion of the dummy wafers havingsmall numbers of times of use with the dummy wafers having large numbersof times of use. For these reasons, the dummy wafers can be usedeffectively without any problem when plasma cleaning is carried out.

Furthermore, in accordance with the present invention, the apparatus canhave a plurality of processing chambers and can transfer wafers anddummy wafers by the same conveyor. Since plasma cleaning can be carriedout by managing the timing of cleaning of each processing chamber by thecontroller, the cleaning cycle can be set arbitrarily, dry cleaning canbe carried out without interrupting the flow of the processing, theprocessing can be efficiently made and the productivity can be improved.

As described above, according to the present invention, there areeffects that the construction of the apparatus is simple, the substratesto be processed are free from contamination and the production yield ishigh.

What is claimed is:
 1. A conveyor system for use in a vacuum processingapparatus, comprising: a first conveyor structure provided with acassette mounter and a first robot; a cassette mount table for holding acassette; and a second conveyor structure for transferring a wafer froma cassette held on the cassette mount table, said wafer being removedfrom the cassette through a window portion of the cassette, wherein: thefirst robot transfers the cassette from the cassette mounter onto thecassette mount table in a state that the window portion of the cassettefaces to the vacuum processing apparatus, the second conveyor structureis provided with a second transfer structure and a second robot arrangedon the second transfer structure, the second robot is shiftable on atrack of the second transfer structure and is provided with an armaccessing the cassette to take out the wafer from the cassette, thesecond robot is arranged to transfer the wafer horizontally from thecassette, and the wafer is adapted to be transferred from the cassetteon the cassette mount table to a vacuum processing chamber by the secondrobot and a third robot in a horizontal line to the extent of onecassette height during transportation of the wafer.
 2. The conveyorsystem according to claim 1, wherein the second transfer structure ismovable in up and down directions.
 3. The conveyor system according toclaim 1, wherein the cassette mount table is arranged such that a set oftwo cassettes is positioned thereon, and the second robot is a solerobot accessing to at least two cassettes.
 4. The conveyor systemaccording to claim 3, wherein the second robot is the sole robotaccessing to a set of lock chambers located next to the second transferstructure.
 5. A conveyor system for use in a vacuum processingapparatus, comprising: a first conveyor structure for transferring acassette, the first conveyor structure being provided with a firstrobot; a cassette table for holding the cassette; a lock chamber; asecond conveyor structure for transferring a wafer from the cassette onthe cassette table to the lock chamber; and a controller controllingsaid first conveyor structure, the second conveyor structure andmanaging a replacement of the cassette on the cassette table.
 6. Theconveyor system according to claim 5, wherein the first conveyorstructure is provided with a cassette mounter, and the first robot isfor transferring the cassette from the cassette mounter to the cassettetable.
 7. The conveyor system according to claim 5, wherein the secondconveyor structure is provided with a second robot, and the secondconveyor structure is disposed between the cassette mount table and thelock chamber.
 8. The conveyor system according to claim 7, wherein eachof the first and second robots has an arm which moves horizontally androtationally.
 9. The conveyor system according to claim 7, wherein eachof the first and second robots moves in up and down directions.